Preheat the oven to 350ºF. Line a baking sheet with a silpat or parchment paper.
In a large bowl, whisk together the flour, baking powder, baking soda, and salt. Set aside.
In the bowl of a stand mixer fitted with the paddle attachment, cream the butter and sugars together until light and airy, about 4 minutes. Add the eggs one at a time, beating for 30 seconds after each addition, and scraping down the sides of the bowl as necessary. Add the vanilla and beat for 30 more seconds to combine.
Add the flour mixture to the butter mixture and mix at low speed until just combined, about 30 seconds.
With the bittersweet chocolate still in its wrapper, break it into small chunks no larger than ½ inch. Unwrap the chocolate and add the broken chocolate as well as the semisweet chips to the dough. Mix on low speed until just combined, about 1 minute.
Cover the dough and refrigerate until cold, at least 1 hour and up to overnight.
Roll dough into 1 inch balls and place 3 inches apart on prepared baking sheet.
Bake 14-16 minutes or until cookies are golden on the edges but still soft in the middle. Let cool on the pan for 3 minutes, then remove to a cooling rack to cool completely.
Cookies will keep in a covered container at room temperature for 3 days.